| The tetraploid hybrid wheatgrass is an excellent forage from chromosome doubling of interspecific hybrids by a cross of diploid A. mongolicum Keng ×A. cristatum cv. ’Fairway’. It has the characteristics of A. mongolicum Keng such as cold and drought resistance,wide adaptability,and that of A. cristatum cv.’Fairway’such as large leaves weight,high grass and seed yield,strong lodging resistance,and high regeneration and tillering ability. In the present study,using F2 segregation population of tetraploid hybrid wheatgrass as materials,we constructed a high density genetic linkage map based on AFLP and SSR molecular markers, and identified the QTLs for 11 important agronomic traits such as plant height, tiller number and leaf stem ratio,in order to lay a foundation for map-based cloning, functional analysis and molecular marker assisted breeding of excellent trait of tetraploid hybrid wheatgrass such as resistance and yield. The main results were as follows:1. A total of 32 AFLP and 30 SSR suitable primers were screened and amplified the genomic DNA of 347 individuals of F2 segregation population of tetraploid hybrid wheatgrass and their parents. A total of 766 polymorphic loci were detected by the PCR amplification,including 581 AFLP and 185 SSR markers.2. The analysis of marker segregation distortion showed that a total of 91 AFLP and 55 SSR markers deviated from 3:1 Mendelian segregation ratio, which accounted for 11.90% of all the AFLP markers and 7.18% of all the SSR markers,respectively. The segregation ratio of AFLP and SSR markers was 19.08%, which met the requirement of no more than 30% distorted markers in plant genetic map.3. We constructed a high density molecular genetic linkage map of tetraploid hybrid wheatgrass with 766 markers. The total length of 14 linkage groups was 2574.3 cM,and the average distance between markers was 3.82 cM.4. The correlative analysis showed that the 11 agronomic traits had positive or negative correlative relationships, of which 8 groups leaf length and plant height, leaf length and stem diameter, stem-leaf ratio and leaf number, stem-leaf ratio and stem diameter, stem-leaf ratio and plant fresh weight, plant dry weight and leaf length, plant dry weight and leaf width, and plant dry weight and tiller number showed positive correlation; 2 groups tem-leaf ratio and tiller number, stem-leaf ratio and leaf length showed negative correlation; 7 groups stem-leaf ratio and plant height, panicle length and stem diameter, panicle length and leaf width, plant dry weight and stem diameter, plant dry weight and plant fresh weight, plant fresh weight and leaf length, and plant fresh weight and leaf width showed significant positive correlation;and one group stem diameter and tiller number showed significant negative correlation.5. A total of 136 QTLs for 11 agronomic traits of tetraploid hybrid wheatgrass were located, which were distributed on the 14 linkage groups,with an average of 9.7 QTLs for each linkage group.6. Of all the 136 QTLs,24 QTLs controlled leaf length,22 QTLs controlled leaf number,16 QTLs controlled plant height,16 QTLs controlled tiller number,14 QTLs controlled plant dry weight,6 QTLs controlled plant fresh weight,3 QTLs controlled leaf width,11 QTLs controlled stem diameter,8 QTLs controlled stem-leaf ratio,3 QTLs controlled panicle length, and 13 QTLs controlled panicle width, which could explain the phenotypic variation from 4.4% to 43.6%,5.6% to 36.6%,5.5% to 36.2%,6.2% to 33.6%, 4.1% to 34.8%,6.2% to 31.0%,10.8% to 29.7%,7.1% to 35.4%,9.5% to 36.1%,8.9% tol5.3%, and 6.9% to 38.3%, respectively.7. A total of 23 QTLs co-localized with a molecular marker, of which 14 co-localized with AFLP markers and 9 with SSR markers. In addition,6 QTLs showed the additive effect, accounted for 4.4%; 21 QTLs showed partial dominant effect, accounting for 15.4%; 40 QTLs showed dominant effect, accounting for 29.4%; and 69 QTLs showed super dominant effect, accounting for 50.7%. |
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